1. Field of the Invention
The present invention relates to a mold assembly, and methods of mounting and removing an insert or inserts thereof, method of ejecting the insert, and more particularly to mold assemblies useful for molding and the like of optical parts including lenses.
2. Description of the Related Art
In the mold assembly for injection molding out of the conventional mold assembly, in exchanging the molds, common parts are left as they are, without exchanging the mold as a whole, only some parts are exchanged, thereby trying to simplify the exchange work, decrease the mold cost, reduce stock space for molds, etc.
Examples of the conventional mold assembly as described above are disclosed in Japanese Patent Publication (Laid-Open) Nos. 60-245512, 60-245525 and 60-245528. These mold assemblies are concerned with a mold assembly for exchanging square-shaped inserts. The inset is inserted into an insert receiving recess provided on a mold body, and thereafter, the insert is moved in a direction parallel to a parting line of the mold, whereby the insert is pressed against a corner portion of the insert receiving recess, so that the insert can be positioned by two inner surfaces of the recess.
According to the above-described conventional technique, since the insert is moved in the direction parallel to the parting line in the insert receiving recess of the mold body to be positioned, the clearance between the insert and the insert receiving recess in this direction must be large. Pieces be molded by the above-described conventional mold assembly are limited to ones which are out of question even if the part for molding is movable in the direction parallel to the parting line, some molded pieces cannot be molded in a predetermined way, if the part for molding is made movable in this direction.
One example of the above is a case where the molded piece is a lens. When an insert for molding a lens is coupled into an insert coupling portion provided in the mold body so as to be movable in the direction parallel to the parting line, lens molding with high accuracy cannot be achieved. For this reason, in the above-described case, mounting and removing of the inserts with respect to the mold body should be contrived such that lens molding with a predetermined accuracy can be performed. For example, with the mold for lens molding, such an arrangement is required that, when only the insert is moved in a direction perpendicular to the parting line, positioning and clamping can be performed.
Since lenses are multiple types and small quantity products for producing lenses having various curvatures in a large number, there are a large number of inserts and many exchanges are performed. In order to reduce the molding cost and increase the production efficiency under the above-described conditions, it is necessary to automate the insert exchange, and contrivance of the above-described mounting of the insert to the mold body and removing it therefrom is required to be suitable for performing the automatic insert exchange.
In the mold assembly for injection molding, it is necessary to provide an ejecting means for ejecting a molded piece from a cavity at the time of mold parting in addition to an insert clamp movement means as described above.
When the insert is moved in the direction perpendicular to the parting line in order to mold a lens as described above, in providing these insert clamp movement means and ejecting means on the mold assembly for injection molding, such an arrangement is required that the insert clamp movement means and the ejecting means have reasonable relationships with the direction of movement of the insert.
Now, in the mold assembly for injection molding having a plurality of cavities, corresponding ejecting means are to be provided for the respective cavities. For example, in the mold assembly for molding lenses and the like, biasing and restoring operations by resilient members (springs, etc.) are utilized for pressing the ejecting means and return thereof to the initial positions.
Further, in Japanese Patent Publication (Laid-Open) No. 57-187223, there is disclosed such an ejecting means that a press-out pin and an abutting portion, against which the press-out pin is abutted, are integrally provided at the peripheral end portion of a molded piece such as a plastic lens.
However, in the mold assembly for injection molding having a plurality of ejecting means, for example, when all of the ejecting means are integrally joined together and these ejecting means are operated as a whole to eject molded pieces from the respective cavities, since respective resilient members acting on the ejecting means have pressure variations, and further, pressure distribution acting on the individually provided resilient members is not constant due to dispersions of the molding conditions, etc. of the molded pieces in the cavities, there is a problem in that forces given to the respective ejecting means cannot be made uniform. Further, such problems occur that an ejecting force cannot act on the center of the molded piece for this reason, and further, in this case, resin which has intruded into gaps formed between component parts of the mold at the time of ejecting cannot be separated reliably.
With the plastic lens molded by providing the abutting portion of the press-out pin on the peripheral end portion thereof, which is disclosed in the aforesaid Patent Publication (Laid-Open) No. 57-187223, it becomes necessary to provide fabricating for removing the abutting portion after the molding, and the arrangement of the insert of the mold becomes complicated.